Hey I need some idea on how to fix the no heat situation on my stepsons bonneville. I first thought it was the heater core being stopped up so I flushed it and got it running clean put it back together got the car started up and still no heat. I bleed the system Like I thought I was supposed and still no heat.

I did check to see if the acutator arm is moving and it is. The upper heater core hose is warm but not hot.

So any ideas.

Is the coolant coming up to normal operating temperature? If not, you should replace the thermostat. If the engine is up to normal temp and you don't have heat, the blend door is probably not operating. The 92 Bonneville has a vacuum operated HVAC control system. The vacuum manifold is behind the glove box. There is a write on this forum that explains how to diagnose and fix it. I will look for it in a minute.

Now I have seen the actuator move and heard the door open and shut. It appears that it heating up to operating temp but I am not positive. I think I will try a complete engine flush with a new thermostate and see what happen unless some else has an idea.

Thanks

Josh

Read both of these posts:

https://www.gmforum.com/mechanical-134/climate-control-diagnostic-88-93-a-285427/

https://www.gmforum.com/mechanical-134/default-redirect-cooled-air-late-model-gm-cars-96-2000-a-279092/

Does your car have a temp gage? If so, what does it read when up to full operating temperature?

It reads about 185 on the in dash gauge. Was thinking about doing a flush and replace the thermostat . So those wright ups are for the non electronic system?

Yes, the writes ups are for the vacuum controlled system and should apply directly to your car.

If it was my car, I would start with changing the thermostat.

thanks I think I am going to do that same thing along with a flush . correct me if I am wrong but this car does not have a heat control valve

If you mean some sort of shut off that controls coolant flow to the heater core, no, it does not have one.

Okay I did the flush and replaced the thermostate and now it does get up to 195 but still no heat I guess I will be looking at Vacum lines. I did notice some lines on the engine that need to be replaced.

Start with the vacuum source that starts in the engine bay and connects to the HVAC vacuum manifold. Do you have a vacuum gage? If so, pull the hose off the manifold and see what vacuum you are getting.